Drill pipe joint



March 16, 1943. w. T. CALDWELL. I 2,313,861.

DRILL: PIPE JOINT Filed Feb. 14, 1940 cult to solve.

Patented Mar.16, 1943 OFFICE DRILL PIPE JOINT Walter 'r. Caldwell, Enid, kla., assignor to The George E. Failing Supply Company, Enid, 0kla., a corporation of Oklahoma l 4 Claims.

This invention relates to drill pipe, such as used in connecting a drill bit with a rotary mechanism in the drilling of earth formations.

Drill pipe of this character is made up of sections which are added to as the depth of the hole progresses and are disconnected in stands when it is necessary to withdraw the drilling string. The joints or couplings between the sections provide problems which have been difiiunder the high pressure of the drilling fluid that is circulated therethrough. They must set up tightly to form rigid driving connections and prevent weaving under rotation of the drilling string. It is also essential that the joints be quickly set up and readily broken. Therefore the threaded connections must be relatively loose and free engaging. When the threads are thus constructed the problems of leakage and weaving are aggravated. Attempts have been made to overcome these diiiiculties by providing ground contacts above and below the threaded connection of the joints. For example, the end of the pin is provided with a bevel to engage a bevelled seat in the box for one contact and the pin is provided with a shoulder adapted to engage the end of the box for the other contact, or the second contact is made by tapering a portion of the pin above the threads to fit within a taper at the end of the box.

Joints of this character are expensive to manufacture because of difliculty in grinding in the upper and lower contact areas so that they have the same degree of tightness.- Even though the jointsmay be perfectly made, a film of drilling mud or foreign material between one set of contactareas will prevent engagement of the other contact areas. It is also found that the contact areas do not wear evenly so that when one is tight the other is loose, thereby allowing the joint to weave and perhaps leak.

Therefore, the principalobject of the present invention is to'provide a Joint constructed to overcome the above 'dimculties and whichvwill be fluid-tight and free from weave.

It is also an object of the invention to provide a Joint that may be readily made up and broken with a minimum power; to provide a coupling of larger diameter than the drill pipe for taking the wear when the drilling string tends to rub against the wall of the drill hole; and to provide a construction whereby the ends of the drill pipe sections may be'reversed' when worn.

In accomplishing these and other objects of the invention, as hereinafter pointed out, I have The joints must be liquid-tight n." in) Application February 14, 1940, Serial No. 318,873

provided improved details of structure, the preferred form of which is illustrated in the accompanying drawing, wherein:

Fig. 1 is a longitudinal section through a drill pipe joint or coupling embodying the features of the present invention.

Fig. 21s a detail perspective 'view of the pin and box ends of the joint.

Fig. 3 is an enlarged fragmentary sectionthrough the joint particularly illustrating the loose character of the threads- Referring more in detail to the drawing: I and 2 designate the pin ends of a pair of drill pipesections 3 and 4 that are connected;

by a. coupling or box 5 to form part of a string of drill pipe which connects the rotating mechanism of a drilling rig with a drill bit and provides a duct for delivering drilling fluid under pressure to the drill bit. The drill pipe sections comprise tubular bodies usually of circular crosssection and of convenient length to bereadily manipulated in the drilling rig.

The ends of the tubular bodies are upset exteriorly thereof at points spaced from the ends to provide sufiicient stock for forming integral annular cylindrical portions in which threads 6 are cut so that the threads project radially of the body portion of the pipe with the root faces thereof substantially registering with the outer faces of the body portions of the pipe as shown in Fig. 2. The inner diameter of the ends of the tubular bodyare swedged or upset inwardly as at 'I to provide slightly constricted bores 8 communicating with the bores through the bodies of the sections and to provide greater thickness and rigidity of the metal.

The threads 6 are preferably straight standard square or acme and terminate at a point adjacent the swedged portion! to leave sufficient stock extendingfrom the terminus of the cylindrical portions of the pipe to provide a pilot 9 having a periphery lll'tapering toward the end thereof as clearly shown in the drawing. The length of the pilot, as well as the degree of taper, is important, as later pointed out.

In the illustrated instance the taper is sub.- stantially 9 with respect to the axis of the pilot. To reduce the surface contact of the pilot with its seat the periphery thereof may be provided with spaced annular grooves I i. These grooves allow for relief of anyforeign material that may have collected on the tapers.

The coupling Sis in the form of a cylindrical sleeve of larger outer diameter than the outer diameter of the pipe sections to providesockets 5' at the ends thereof having walls of sumcient thickness to accommodate internally formed threads I2 which cooperate with the threads 6 on the pins, the depth and width of the threads being so related that they are freely engageable and quickly made up when the pin is threaded therein.

. Formed in the sleeve below the sets of threads are seats l3 having the same taper as the pilots the tapers extending smoothly from the terminus of the internal threads to a diameter substantially corresponding to end of the pilots so that the pilots are adapted to be firmly engaged therein to prevent leakage through the joint. Attention is here directed to the fact that the length of the pilots and their seats are such that they provide adequate contacting surfaces to rigidly retain the pin and box in axial alignment without weave incidental to the looseness of the threads. In other words, the threads are primarily depended upon for holding the pin in the box and not to eliminate weave in the joint, this being taken care of by reason of the taper and length of the pilots. Connecting the tapering seats i3 is a bore I4 forming a flow passage between the obvious that a joint has only one ground surface engaging with a pin, thereby simplifying the manufacture and assuring tightness even though the tapers should become worn. The pilot will always find contact with'its seat since there is no collar or other interengaging portion between the body of the pipe and the end of the coupling or box,

,Both ends of the pipe sections are formed in the same manner with a coupling screwed on one end of each section to be permanently retained thereon, however, when the threads or parts of the coupling become worn at the unthreaded end. the pipe sections may be reversed and the unworn connections brought into use. From the foregoing it is obvious that I have provided a simple and relatively inexpensive drill pipe joint which is readily manufactured and adapted to maintain a liquid-tightseal. The long tapers of the pilots stabilize the joint-s and enhance rigidity of the drilling string.

What I claim and desire to secure by Letters Patent is;

1. A drill pipe joint including, a pair of'adjacent pipes each having an integral annular externally enlarged collar portion spaced from adjacent ends thereof and provided with straight threads, tapering pilots on the adjacent ends of the pipes, the interior portion of said pilots being internally upset to provide necessary wall thickness, and a coupling for said pipes having internally threaded sockets in the respective ends thereof for receiving the straight threads of the pipe and having oppositely directed tapered seats for said pilots, said pilots having smooth face portions closely contacting corresponding face portions of the tapered'seats to prevent weaving of the joint incidental to characteristic looseness of straight threads, said pilots having annular grooves between said smooth face portions.

2. In a string of drill pipe, a drill pipe having an integral annular externally enlarged cylindrical portion spaced from each end of the pipe and provided with straight threads having root faces thereof substantially registering with the outer face of the body portion of the pipe and with the ends of the pipe tapering from the terminus of said enlarged portions to form tapering pilots, the interior portion of said pilots being internally upset to provide the necessary wall thickness for the taper, and a box having internally threaded sockets extending inwardly from the respective ends thereof for receiving the straight threads on one end-of said pipe and the corresponding opposite end of an adjoining pipe and having seats tapering smoothly from the terminus of the internal threads to a diameter substantially corresponding with the diameter at the end of the pilots so that the seats are coextensive with and closely contact the pilots to preventweaving of the joint incidental to characteristic looseness of straight threads when the pipes are connected and to effect immediate release of the tapered pilots from the tapered seats.

-3. In a string of drill pipe, a drill pipe having an integral annular externally enlarged cylindrical portion spaced from each end of the pipe and provided with straight threads having root faces thereof substantially registering with the outer face of the body portion of the pipe and with the I ends of the pipe tapering from the terminus of said enlarged portions to form tapering pilots,'

the interior portion of said pilots being internally upset to provide the necessary wall thickness for the taper, and a box having internally threaded sockets extending inwardly from the respective ends thereof for receiving the straight threads on one end of said pipe and the corresponding opposite end of an adjoining pipe and having seats tapering smoothly from the terminus of the internal threads to a diameter substantially corresponding with the diameter at'the end of the pilots so that the seats are coextensive with and closely contact the pilots to prevent weaving of the" joint incidental to characteristic looseness of straight threads when the pipes are connected and to efiect immediate release of the-tapered pilots from the tapered seats, said tapering surfaces of the pilots having spaced annular grooves for reducing the contact of said tapering seats and relieving foreign material that may collect on said tapering surfaces.

4. A drill pipe including a. pair of adjacent pipe forming ducts for flow of drilling fluid under pressure therethrough and having tapered ends forming facing pilotsand provided with straight threads at the base of said tapered pilots, and a coupling having internally threaded sockets extending inwardly from ends thereof to accommodate the threads on the pipe and having tapered .seats at the base of said sockets interconnected acteristic looseness of straight threads and toprovide seals between the through bore and said threads.

WALTER T. CALDWELL. 

